The present invention relates to an image coding device, and more particularly, to a perceptual error processing method and an image coding device for improving image coding efficiency by enhancing an image data correlation by using human color perception in a temporal and spatial area.
A conventional image coding device improves coding efficiency by using the correlation with respect to the input image data and generally employs two coding methods as shown in FIG. 1. The first method is a transform coding method for defining the image data correlation in a spatial frequency area by transforming the image data to be coded from a temporal frequency area to the spatial frequency area using a discrete cosine transform (which is referred to as DCT, hereinafter). This coding method is used in an image compression and coding by extracting only the characteristic of the spatial frequency of the image data without loss of the image data, and more particularly, in the coding of a still image.
The second method is a predictive coding method by a differential pulse code modulation (which is referred to as DPCM, hereinafter). In this method, the amount of movements of the coding images are estimated using vector values by comparing an nth image (O) to be coded which is input from an image input portion 11 as shown in FIG. 1 with an (n-1)th image which was previously coded and estimates an amount of movement of the coded image unit using a vector value, to form a predictive image (P) of an original nth image to be coded using the estimated movement vector. The predictive image formed as above has an error due to the movement when compared with the actual original nth image. Such an error due to the movement is referred to as a predictive error (e) and expressed in the formula (1) EQU e=O-P (1)
The predictive error as defined above means the amount of the image data correlation in the temporal area. Using only the image data formed by this predictive error in the actual coding device causes loss of the image data but improves the efficiency of the image coding. Therefore, a hybrid coding method wherein the DCT method for extracting the spatial correlation between the image data and the DPCM method for extracting the temporal correlation between the image data are both applied is commonly used in the motion image coding method, as shown in FIG. 1.